1. Field of the Invention
The present invention relates to a cooling water recirculation apparatus for an internal combustion engine.
2. Description of the Related Art
In a cooling water recirculation apparatus for an internal combustion engine, heat irradiated from an internal combustion engine body is absorbed by cooling water, and a part of the absorbed heat is utilized as a heat source for a passenger room heater.
For this reason, the cooling water that has flowed through an engine interior cooling water communication passage provided in the internal combustion engine body, i.e., a so-called water jacket and that has been warmed by absorbing the heat from the internal combustion engine body during the passage is fed out from the internal combustion engine body to the passenger room heater through a heater side cooling water recirculation circuit for connecting the internal combustion engine body and the passenger room heater to each other for recirculation.
However, immediately after the starting operation of the internal combustion engine, since the cooling water is less warmed up, the passenger room heater less works.
Accordingly, for instance, Japanese Utility Model Publication Laid-Open No. Sho 59-14706 discloses a technique for providing, in a midway of the heater side cooling water recirculation circuit, a heating device for heating the cooling water by using the exhaust gas of the internal combustion engine as a heat medium, and operating the heating device upon the warming-up operation of the internal combustion engine to heat the cooling water for the passenger room heater. According to this technique, the effect of the passenger room heater upon the starting operation of the internal combustion engine is more enhanced than that of the conventional one.
However, even according to the technique disclosed in the above-described publication, since the cooling water is caused to always flow to the passenger room heater upon the warming operation, an amount of the recirculation of the cooling water is increased. Also, since the heat is radiated in the passenger room heater even if the cooling water is heated by the heating device, the heating efficiency of the overall recirculated cooling water is degraded. As a result, the enhancement of the effect of the heater is not satisfactory.